It's of little secret that Chelsea are lacking depth in defense. Manager Jose Mourinho discussed the situation this weekend, prompting speculation that the Blues are nearing a deal to land either a left back or center back this summer.

"Five is not enough. That's obvious. We cannot go to the Premier League with five defenders," Mourinho told reporters. "That's our weakness. The quality is good, but the numbers are not enough."

Everton's John Stones, a 21-year-old center back who also plays right back, had been considered high on Chelsea's wish list. But ESPN reports that Mourinho hinted that Chelsea may not increase their offer, citing his comment of knowing "when we have to stop and turn to another side and think in another option." Chelsea had reportedly bid over £20 million for Stones, but Everton was firmly against letting their most promising defender leave.

Plan B appears to be Baba Rahman. The 21-year-old left back has made 31 appearances for FC Augsburg, and 11 appearances for Ghana. German publicaton Bild reported Saturday that Chelsea and Augsburg had agreed to a £17.6-million fee. ESPN reported that Augsburg manager Markus Weinzierl wants Rahman's situation to be cleared up soon. Perhaps a sticking point might be playing time, with Cesar Azpilicueta expected to take up much of the first-team duties. It's possible that Chelsea may also add a versatile and experienced reserve who can usurp Rahman as Azpilicueta's favored backup. 

Last week, The Sun reported that Galatasaray left wingback Alex Telles was a Chelsea target. The 22-year-old Brazilian made 37 appearances for the Turkish club after beginning his professional career with 38 total appearances with Juventude and Gremio.

Azpilicueta, 25, and reserve center back Kurt Zouma, 20, are the only defenders under the age of 29 on the Chelsea roster, which may prompt Mourinho to seek some youth. Mourinho may also consider giving versatile Dutch defender Nathan Ake more time on the pitch. The promising 20-year-old has only five appearances for Chelsea, but received some experience on loan with Reading in March.  

While adding a young defender or two may be what Mourinho needs to provide some flexibility to the backline, it seems unlikely that the rotation will change much in 2015-2016. At the risk of late-season fatigue, veterans Branislav Ivanovic (31), Gary Cahill (29) and John Terry (34) are still expected to receive a significant portion of the first-team duties.